Optical microlithography is the process in semiconductor manufacturing in which chip designs are patterned onto silicon wafers. Currently, the semiconductor industry uses tools with a light wavelength of 248 nm from a KrF excimer laser to create chips with feature sizes as small as 180 nm. The next state of the art technology will make use of 193 nm light from an ArF laser, and is expected to extend optical lithography to chip features as small as 100 nm.
Although it is assumed that some non-optical lithography (X-ray, extreme ultraviolet, electron-beam, etc.) will ultimately replace optical lithography, no such technology is expected to be ready within the next decade. Thus, interest in 157 nm lithography has exploded in recent months, and it is now viewed as a critical bridge across the gap between optical and non-optical lithographies. Development of technology using 157 nm light from a F2 laser will extend the use of optical lithography to at least the 70 nm node.
The imaging layer used in microlithography is a photoresist, which must be nearly transparent to the wavelength of light employed. The basic requirements for a single layer resist also include good plasma etch resistance, high Tg, compatibility with conventional aqueous base developer, and imaging with favorable development/dissolution characteristics. Alternatively, etch resistance can be provided by the substrate on which the photoresist is coated (sometimes referred to as a “hard mask”). This strategy is utilized when the opacity of the resist precludes using it as a thick, single layer resist.
A need exists for bilayer or multilayer resists that are suitable for 157 nm imaging.